After moving to the United States in the early 1960s, Patterson worked mainly on television. In 1960, he was cast in two episodes of the ABC/Warner Brotherswesterntelevision seriesThe Alaskans, starring Roger Moore. Patterson played Tom Kirk in the episode "Behind the Moon" and Jeff Warren in "Sign of the Kodiak", a reference to the Kodiak bear. Later that year, he was cast as the fictional detective Dave Thorne on another ABC/WB series, Surfside 6, set on a houseboat anchored at Miami Beach, Florida. His co-stars during the two-year run of Surfside 6 from 1960 to 1962 were Van Williams as Kenny Madison, Troy Donahue as Sandy Winfield, II, Diane McBain as socialite Daphne Dutton, and Margarita Sierra as the singer Cha Cha O'Brien. After Surfside 6 folded, Donahue was transferred to another ABC/WB series, Hawaiian Eye, which aired its fourth and final season from 1962 to 1963. Early in 1966 Patterson appeared on Perry Mason as Dan Thorne in "The Case of the Midnight Howler."

Patterson was one of the handful of prime time and film performers to appear on daytime serials prior to 1970. His first soap opera role was that of Brad Kiernan on ABC's The Nurses. After that show was cancelled in 1967, he joined the original cast of One Life to Live, a move which reunited Patterson with Doris Quinlan, the producer of The Nurses.

Patterson remained on One Life to Live until 1970, when his character Joe Riley was presumed dead; he returned to the show in 1972 and remained the romantic lead until 1979, when he left due to his unhappiness with the direction the show took after Doris Quinlan left to produce NBC's troubled serial The Doctors. Patterson then joined the cast of NBC's Another World and Texas in the role of Dr. Kevin Cook. The character began on Another World, but moved to Texas when that show began on August 4, 1980. He stayed until 1981 when the show revamped to bring up its poor ratings against the number one daytime program, ABC's General Hospital. Texas was cancelled in 1982. Patterson returned to One Life to Live as Joe's twin brother, Tom Dennison, from 1986 until 1988. He also continued to make appearances in other television shows such as War and Remembrance, Magnum, P.I. and The A-Team, and appeared in movies including Chato's Land (1972) and Airplane II: The Sequel (1982). His last role was Sergeant Gaylor in the 1994 film, Healer.